$$\frac{1}{k^{2}}+\frac{1}{2^{2}}+\frac{1}{M^{2}}=\frac{1}{kk}+\frac{1}{2M}+\frac{1}{kM}+\frac{1}{kM},x^{3}+2^{3}+M^{3}=3222M=$$
$x=\sqrt[3]{-M^{3}+3222M-8}$
$k=\frac{8M}{M^{2}-2M+4}\text{ and }M\neq 0$
